Optical recording medium, optical recording medium manufacturing apparatus, and optical recording medium manufacturing method

ABSTRACT

In an optical recording medium  10  comprising groove tracks  11  including a first area Ba for recording record information and a second area Ca in which predetermined data is formed as embossed pit rows  19  and a readout of other data overwritten and recorded on said embossed pit rows  19  is prevented, and land tracks  12  formed between the adjacent groove tracks  11 , a depth Ed and a duty of the embossed pit rows  19  are set so that a radial push-pull signal in the first area and a radial push-pull signal in the second area become the substantially same level.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to an optical recording mediumcapable of optically recording record information, an optical recordingmedium manufacturing apparatus for forming such an optical recordingmedium and an optical recording medium manufacturing method for formingsuch an optical recording medium.

[0003] 2. Description of the Related Art

[0004] At present, a reproduction-only DVD-Video disk on which contentsare previously recorded and a DVD-RW (DVD Re-recordable) disk as anoptical recording medium capable of optically recording recordinformation have been known. FIG. 13 shows a main enlarged view of sucha DVD-RW disk and specifically shows an enlarged view of a boundaryportion between a buffer zone (area of a direction of an arrow Ba in thedrawing) within a read-in area and a control data zone placed in thejust front thereof (area of a direction of an arrow Ca in the drawing).Incidentally, for the purpose of making a disk structure easy tounderstand, in FIG. 13, upper and lower surfaces of the disk aredepicted in reverse.

[0005] As shown in FIG. 13, according to the DVD-RW disk, in a firstarea such as the buffer zone or data area in which record information isrecorded, groove tracks 1 having a depth Gd [nm] for recording therecord information are meanderingly formed and land pre-pits 3 forgenerating various information such as an address are formed on landtracks 2 located between the adjacent groove tracks 1. Also, accordingto the DVD-RW disk, in order to prevent an illegal copy of the DVD-Videodisk by means of bit by bit, control information recorded thereon isformed into embossed pit rows 4 having the same depth Gd [nm] as that ofthe groove tracks 1 to be recorded in the control data zone and thegroove tracks become an intermittent state.

[0006] According to the DVD-RW disk as described above, since theembossed pit rows 4 are embedded in the control data zone, in case thatthe illegal copy of the DVD-Video disk is made by means of bit by bit,readout of data overwritten in the control data zone is prevented by areproduction output through the embossed pit rows 4 to disable theillegal copy. However, in the DVD-RW disk constructed thus, the embossedpit rows 4 are formed, so that a radial push-pull signal level in thecontrol data zone (a second area) decreases with respect to a radialpush-pull signal level in other first area in which the recordinformation is recorded and a problem of causing instability ofoperation of a tracking servo circuit or a spindle servo circuit in arecording and reproducing apparatus has arisen.

SUMMARY OF THE INVENTION

[0007] The invention is implemented in view of the problem, and anobject of the invention is to provide an optical recording mediumcapable of obtaining a constant radial push-pull signal over the wholeregion of a disk and stably maintaining an operation of a servo circuitin a recording and reproducing apparatus, an optical recording mediummanufacturing apparatus and an optical recording medium manufacturingmethod for forming such an optical recording medium.

[0008] In order to solve the problem, according to a first aspect of theinvention, there is provided an optical recording medium capable ofoptically recording record information, comprising:

[0009] a first region formed continuous groove tracks thereon to berecorded the record information; and

[0010] a second region formed discontinuous embossed pit rows thereon inaccordance with predetermined data,

[0011] wherein the embossed pre-pits rows prevents from reproducing dataoverwritten on the second region; and

[0012] a level of a radial push-pull signal of the second region is notsmaller than about 80% of a level of a radial push-pull signal of thefirst region.

[0013] According to a second aspect of the invention, there is providedthe optical recording medium according to the first aspect of theinvention, wherein the groove tracks and the embossed pit rowssubstantially satisfy the following mathematical equation

Duty=0.04(Ed−λ/8n)²+(−0.07Gd²+6Gd−35.6)

[0014] where Duty [%] is an average duty of the embossed pit rows, Ed[nm] is a depth of the embossed pit rows, λ [nm] is a wavelength of alight beam, and n is a refractive index of a substrate of the opticalrecording medium, and Gd [nm] is a depth of the groove track.

[0015] According to a third aspect of the invention, there is providedan optical disk master manufacturing apparatus for manufacturing anoptical disk master for manufacturing an optical recording mediumcapable of optically recording record information, the optical recordingmedium comprising a first region formed continuous groove tracks thereonto be recorded the record information and a second region formeddiscontinuous embossed pit rows thereon in accordance with predetermineddata, wherein the embossed pre-pits rows prevents from reproducing dataoverwritten on the second region and a level of a radial push-pullsignal of the second region is not smaller than about 80% of a level ofa radial push-pull signal of the first region, the apparatus comprising:

[0016] a light beam generator for forming a plurality of regions on theoptical disk master corresponding to the first and second regions of theoptical recording medium; and

[0017] a controller for controlling the light beam generator.

[0018] According to a fourth aspect of the invention, there is providedthe optical disk master manufacturing apparatus according to the thirdaspect of the invention, wherein the groove tracks and the embossed pitrows of the optical recording medium substantially satisfy the followingmathematical equation

Duty=0.04(Ed−λ/8n)²+(−0.07Gd²+6Gd−35.6)

[0019] where Duty [%] is an average duty of the embossed pit rows, Ed[nm] is a depth of the embossed pit rows, λ [nm] is a wavelength of alight beam, and n is a refractive index of a substrate of the opticalrecording medium, and Gd [nm] is a depth of the groove track.

[0020] According to a fifth aspect of the invention, there is providedan optical disk master manufacturing method for manufacturing an opticaldisk master for manufacturing an optical disk master for manufacturingan optical recording medium capable of optically recording recordinformation, the optical recording medium comprising a first regionformed continuous groove tracks thereon to be recorded the recordinformation and a second region formed discontinuous embossed pit rowsthereon in accordance with predetermined data, wherein the embossedpre-pits rows prevents from reproducing data overwritten on the secondregion and a level of a radial push-pull signal of the second region isnot smaller than about 80% of a level of a radial push-pull signal ofthe first region,

[0021] the method comprising the steps of forming a plurality of regionson the optical disk master corresponding to the first and second regionsof the optical recording medium.

[0022] According to a sixth aspect of the invention, there is providedthe optical disk master manufacturing method according to the fifthaspect of the invention, wherein the groove tracks and the embossed pitrows of the optical recording medium substantially satisfy the followingmathematical equation

Duty=0.04(Ed−λ/8n)²+(−0.07Gd²+6Gd−35.6)

[0023] where Duty [%] is an average duty of the embossed pit rows, Ed[nm] is a depth of the embossed pit rows, λ [nm] is a wavelength of alight beam, and n is a refractive index of a substrate of the opticalrecording medium, and Gd [nm] is a depth of the groove track.

BRIEF DESCRIPTION OF THE DRAWINGS

[0024]FIG. 1 is a diagram showing a structure of an information recordsurface of a DVD-RW disk.

[0025]FIG. 2 is a diagram showing a structure of a read-in area of theDVD-RW disk.

[0026]FIG. 3 is a diagram showing a record format of pre-informationpreviously recorded on the DVD-RW disk.

[0027]FIG. 4 is a diagram showing a structure of a record surface of aDVD-RW according to an embodiment.

[0028]FIG. 5 is a main block diagram of a recording and reproducingapparatus.

[0029]FIG. 6 is a graph in which a relation of a radial push-pull signallevel to a depth Gd of groove tracks and a depth Ed of embossed pitrows.

[0030]FIG. 7 is a graph showing a relation between a depth Ed and anaverage duty ratio of the embossed pit rows for obtaining the sameradial push-pull signal level in case that the depth Gd of the groovetracks is set at 10 nm.

[0031]FIG. 8 is a graph showing a relation between a depth Ed and theaverage duty ratio of the embossed pit rows for obtaining the sameradial push-pull signal level in case that the depth Gd of the groovetracks is set at 20 nm.

[0032]FIG. 9 is a graph showing a relation between a depth Ed and theaverage duty ratio of the embossed pit rows for obtaining the sameradial push-pull signal level in case that the depth Gd of the groovetracks is set at 30 nm.

[0033]FIG. 10 is a graph showing a relation between a depth Gd of thegroove tracks and each of minimum values f (Gd) in which the averageduty ratio of the embossed pit rows shown in FIGS. 7 to 9 becomes aminimum.

[0034]FIG. 11 is a schematic configuration diagram of an opticalrecording medium manufacturing apparatus according to the invention.

[0035]FIG. 12 is an operational flowchart of the optical recordingmedium manufacturing apparatus.

[0036]FIG. 13 is a diagram showing a structure of a record surface of aDVD-RW disk according to a related art.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0037] A preferred embodiment of the invention will be described withreference to the drawings. Incidentally, an embodiment in case ofapplying the invention to a DVD-RW disk (hereinafter, abbreviated asDVD-RW) which is one of optical recording media capable of opticallyrecording record information will be described.

[0038] First, a record format of the DVD-RW will be described withreference to FIGS. 1 to 3. Incidentally, FIG. 1 is a diagram showing aphysical record area on the DVD-RW after video information is recordedaccording to the DVD-RW format.

[0039] As shown in FIG. 1, in an information area of the DVD-RW, aread-in area, a data area and a read-out area are sequentially recordedfrom a start point of the information area (a start point of a physicalsector) toward the outside in a radial direction. The read-in area is anarea first accessed at the time of recording and reproducing the DVD-RW,and physical information about such a DVD-RW, for example, a disk size,a minimum readout rate or a disk structure is recorded. The data area isan area in which contents, namely record information is mainly recorded.For example, as the contents to be recorded, there are image data, voicedata, data capable of being read by a computer, programs, or the like.The read-out area is an area following the data area, and data [00h]indicating the record end is recorded for a predetermined period.

[0040]FIG. 2 is a diagram showing a structure in the read-in area. Theread-in area has an initial zone in which the data [00h] is recorded, areference code zone in which data for generating a particular channelbit pattern (3T-6T-7T) is recorded, a buffer zone 1 in which data [00h]is recorded, a control data zone in which various control information isrecorded, and a buffer zone 2 for leading to a data area in which data[00h] is recorded.

[0041] Such a control data zone is located at the same address as thatof the control data zone in the DVD-Video disk as described above andcontrol information previously recorded in this zone is formed intoembossed pit rows to be embedded. Therefore, in this zone, in case thatother data is overwritten and recorded, readout of the data is preventedby a reproduction output through the embossed pit rows.

[0042] Next, a record format of pre-information previously recorded onthe DVD-RW will be described with reference to FIG. 3. Incidentally, inFIG. 3, the upper stage shows a record format in record information, anda waveform of the lower stage shows a wobbling waveform indicating awobbling state (a plan view of groove tracks) of groove tracks 11 forrecording the record information. Also, in FIG. 3, upward arrows betweenthe record information and the wobbling waveform schematically showpositions in which pre-pits are formed. Also, the wobbling waveformshown in FIG. 3 is illustrated to be an amplitude thereof greater thanan actual amplitude in order to facilitate understanding.

[0043] The record information recorded on the DVD-RW is divided intoevery synchronous frame acting as information unit previously as shownin FIG. 3. One synchronous frame is constructed to have a length to be1488 times (1488T) as large as a channel bit length (hereinafter calledT) defined by a record format in case of recording the recordinformation, and a front portion having 32T in length of one synchronousframe is used as synchronous information SY for synchronization everysynchronous frame.

[0044] The pre-information recorded on the DVD-RW is recorded everysynchronous frame. When the pre-information is recorded on the DVD-RW,one pre-pit B2 acting as indicator of a synchronous signal in thepre-information is always formed on a land track adjacent to an area inwhich the synchronous information SY of the synchronous frame isrecorded, and two or one pre-pits (B1, B0) acting as indicator of thecontents of the pre-information to be recorded are formed on a landtrack adjacent to a first half portion in the synchronous frame otherthan the synchronous information SY.

[0045] Normally, the pre-information is recorded by forming the pre-pitsin even-numbered synchronous frames (hereinafter called “EVEN frame”).That is, in FIG. 3, the pre-pits (showed by upward arrows of solid linesin FIG. 3) are formed in the EVEN frame and the pre-pits are not formedin an ODD frame adjacent to the EVEN frame. More specifically, when thepre-pits are formed in the EVEN frame, in the synchronous frame of thehead of a recording sector, all the pre-pits (pre-pits B2, B1 and B0)are formed, and in the synchronous frame other than the head of therecording sector, the pre-pits B2 and B0 are formed when thepre-information to be recorded in the synchronous frame is “1” and onlythe pre-pit B2 is formed when the information to be recorded is “0”.

[0046] On the other hand, when the pre-pits are formed in odd-numberedsynchronous frames (hereinafter called “ODD frame”), in the synchronousframe of the head of a recording sector, the pre-pits B2 and B1 areformed, and in the synchronous frame other than the head of therecording sector, the pre-pits are formed in a manner similar to thecase of the EVEN frame.

[0047] It is determined which synchronous frames of the EVEN frames/ODDframes the pre-pits are formed depending on positions of the pre-pitsformed previously on the adjacent land track. That is, the pre-pits aregenerally formed in the EVEN frames, but in case of forming the pre-pitsin the EVEN frames, when the pre-pits are close to the pre-pits on theadjacent land track formed previously in a radial direction of a disk,the pre-pits are formed in the ODD frames. By forming the pre-pits thus,the pre-pits are absent in a position of the adjacent land track, sothat an influence due to crosstalk can be avoided in case of detectingthe pre-pits.

[0048] On the other hand, the groove tracks are wobbled at a constantwobbling frequency f0 (frequency holding eight waves of wobble signalsin one synchronous frame) of 140 kHz over all the synchronous frames. Byextracting this constant wobbling frequency f0, a recording andreproducing apparatus detects a signal for rotation control of a spindlemotor or generates a clock signal for recording.

[0049] Next, a structure of a record surface of a DVD-RW 10 according tothe embodiment of the invention will be described with reference to FIG.4. FIG. 4 shows a boundary portion between a buffer zone (Ba) in theread-in area and a control data zone (Ca) placed in just front of thisbuffer zone in a manner similar to FIG. 13 described above.

[0050] The DVD-RW 10 comprises a multi layer 14 formed of a record layermade of a phase change material (for example, GeSbTe) acting as a datarecord layer and a protective layer of a glass material (ZnS-SiO2)sandwiching this record layer, and constructs a phase change typeoptical recording medium. A reflection layer 15 for reflecting a lightbeam (B) at the time of data reproduction is formed below the multilayer 14 and further below the reflection layer, a transparent substrate(polycarbonate) 17 is bonded by an adhesive layer 18. Also, atransparent film (polycarbonate) 16 for protecting the multi layer 14 isprovided in an incident surface side of the light beam (B).

[0051] As shown in FIG. 4, in an area (first area) such as a buffer zoneother than control data, in a manner similar to the DVD-RW diskaccording to the related art shown in FIG. 13, the DVD-RW 10 is formedgroove tracks 11 having a depth Gd of about 30 [nm] as an informationrecord track, land tracks 12 between the adjacent groove tracks 11, andland pre-pits 13 having the same depth as that of the groove tracks 11are formed on the land tracks 12.

[0052] Also, the DVD-RW 10 is formed embossed pit rows 19 having theaverage duty of 80%, land tracks 12, and land pre-pits 13 in the controldata zone (second area) in a manner similar to the DVD-RW disk accordingto the related art. However, according to the DVD-RW 10 of theembodiment, the embossed pit rows 19 are formed at a depth Ed (50 nm)deeper than the depth Gd (30 nm) of the groove tracks 11.

[0053] This is performed in order to match a radial push-pull signallevel in the control data zone, namely the second area with a radialpush-pull signal level in the first area for recording other recordinformation, and various conditions of the embossed pit rows 19 formatching the levels of the radial push-pull signals will be describedbelow in detail with reference to FIGS. 5 and 6.

[0054]FIG. 5 is a main block diagram of a recording and reproducingapparatus 80. A configuration and operation of the recording andreproducing apparatus 80 will be described with reference to FIG. 5.

[0055] The recording and reproducing apparatus 80 comprises a beamsplitter 61 for reflecting a laser beam to guide the laser beam to anobjective lens 60 and also transmitting a light beam reflected by arecord information surface of the DVD-RW 10 to guide the light beam to aphotodetector 62, an objective lens 60 for gathering the light beamreflected by the beam splitter 61 to focus on the record informationsurface of the DVD-RW 10, a radial push-pull type photodetector 62 fordetecting the light quantity of the light beam reflected by the recordinformation surface of the DVD-RW 10 with four light receiving elementsA to D, and a computation processing part 76 for computing andprocessing a light-to-current conversion signal outputted from thephotodetector 62.

[0056] The drawing within a circle in FIG. 5 schematically shows asituation in which the reflected light of the light beam applied on thegroove tracks 11 and the pre-pits 13 is detected by the photodetector62, and the photodetector 62 is placed on a centerline of the groovetracks 11 and detects the reflected light on the groove tracks 11 by thefour light receiving elements A to D. The recording and reproducingapparatus 80 is constructed so as to obtain a tracking error signal, anRF signal and a pre-pit signal described below by computing andprocessing the light-to-current conversion signal outputted from thefour light receiving elements A to D of this photodetector 62 by thecomputation processing part 76.

[0057] The computation processing part 76 comprises four current/voltageconverters 63 to 66, five adders 67 to 70 and 72, a subtracter 71, alow-pass filter (LPF) 73, a high-pass filter (HPF) 74, and a comparator75. Each of output signals A to D of the photodetector 62 is supplied tothe four current/voltage converters 63 to 66 and is converted from acurrent value to a voltage value by each of the current/voltageconverters 63 to 66. Output signals of the current/voltage converter 63and the current/voltage converter 66 are added by the adder 67. Also,output signals of the current/voltage converter 64 and thecurrent/voltage converter 65 are added by the adder 69. Then, outputsignals of the adder 67 and the adder 69 are subtracted by thesubtracter 71 and are outputted from the subtracter 71 as a radialpush-pull signal in a form of (A+D)−(B+C). In this radial push-pullsignal, a pre-pit signal component is removed by the LPF 73 and anoutput is produced as a tracking error signal. Also, in the radialpush-pull signal outputted from the subtracter 71, a tracking errorsignal component is removed by the HPF 74 and further a comparison witha predetermined reference level is performed by the comparator 75 andwhereby an output is produced as a pre-pit detection signal.

[0058] On the other hand, output signals of the current/voltageconverter 63 and the current/voltage converter 64 are added by the adder68. Also, output signals of the current/voltage converter 65 and thecurrent/voltage converter 66 are added by the adder 70. Then, outputsignals of the adder 68 and the adder 70 are added by the adder 72 andare outputted from the adder 72 as an RF signal in a form of(A+B)+(C+D).

[0059] In the recording and reproducing apparatus 80, when recordinformation is recorded on the DVD-RW 10, rotation control of the DVD-RW10 is performed at a predetermined rotational speed by extracting awobbling frequency of the groove tracks 11 and also pre-information isacquired in advance by detecting the pre-pits 13 and based on thatinformation, the optimum output of a light beam acting as record lightis set. Also, in the recording and reproducing apparatus 80, addressinformation indicating a position on the DVD-RW 10 to be recorded recordinformation is acquired by detecting the pre-pits 13 and based on thisaddress information, the record information is recorded in a desiredposition.

[0060] The recording and reproducing apparatus 80 applies a light beamcorresponding to the record information to the groove tracks 11 andforms information pits on the groove tracks 11. At this time, as shownin FIG. 4, a size of a light spot (SP) is set so that the light spot isapplied to not only the groove tracks 11 but also the pre-pits 13 formedon the land tracks 12. Therefore, the recording and reproducingapparatus 80 can detect the pre-pits 13 to acquire the pre-informationbased on the radial push-pull signal generated by detecting thereflected light of the light spot (SP).

[0061]FIG. 6 is a graph in which a relation of a radial push-pull signallevel to a depth Gd of groove and a depth Ed of embossing formed in theDVD-RW 10 is obtained by simulation, and an axis of abscissa shows thedepth Gd of the groove and the depth Ed of the embossing and an axis ofordinate shows a radial push-pull signal. A curve shown by a dotted linein FIG. 6 shows a relation of a radial push-pull signal level Vg to thedepth Gd of the groove tracks 11 and a curve shown by a solid line showsa relation of the radial push-pull signal level Ve to the depth Ed ofthe embossed pit rows 19 having 80% in the average Duty ratio. A curveshown by a chain line in FIG. 6 shows a relation of a radial push-pullsignal level Ve to the depth Ed of the embossed pit rows 19 having 50%in the average Duty ratio.

[0062] As described above, according to the DVD-RW shown in FIG. 13,both of the depth Gd of the groove tracks 1 and the depth Ed of theembossed pit rows 4 are formed at about 30 nm, so that a radialpush-pull signal level in the groove tracks 1 is about 0.42 and a radialpush-pull signal level in the embossed pit rows 4 is about 0.32 as shownin FIG. 6. That is, the radial push-pull signal level in the embossedpit rows 4 decreases to about 76% with respect to the radial push-pullsignal level in the groove tracks 1.

[0063] When both the depth of the groove tracks 1 and the depth of theembossed pit rows 4 are formed in 30 nm and the average Duty ratio ofthe embossed pit rows is formed in 50%, the radial push-pull signallevel Vg in the groove tracks 1 is about 0.42 and the radial push-pullsignal level Ve in the embossed pit rows 4 is about 0.2. That is, theradial push-pull signal level Ve in the embossed pit rows 4 is reducedabout 48% of the radial push-pull signal level Vg in the groove tracks1.

[0064] On the other hand, according to the DVD-RW 10 of the embodiment,a depth Gd of the groove tracks 11 is formed at about 30 nm and a depthEd of the embossed pit rows 19 is formed at about 50 nm. Therefore, asshown in FIG. 6, the radial push-pull signal level in the embossed pitrows 19 increases to about 0.42 to be substantially equal to a radialpush-pull signal level in the groove tracks 11.

[0065] As described above, in the case of forming the groove tracks 11at the depth Gd of about 30 nm, the radial push-pull signal level Vg inthe groove tracks can be set substantially equal to the radial push-pullsignal level Ve in the embossed pit rows when the embossed pit rows 19having the average duty of 80% are formed at the depth Ed of about 50nm. However, the invention is not limited to these numeric values of thedepth Gd of the groove tracks, the average duty, and the depth Ed of theembossed pit rows. In order to be the radial push-pull signal level Vein the embossed pit rows not smaller than about 80% of the radialpush-pull signal level Vg in the groove tracks , relation among thedepth Gd of the groove tracks, the average duty, and the depth Ed of theembossed pit rows will be described below with reference to FIGS. 7 to9.

[0066] In FIGS. 7 to 9, when a depth Gd of the groove tracks is fixed ata predetermined depth, a relation between a depth Ed and the averageduty ratio of the embossed pit rows for obtaining the radial push-pullsignal level in the embossed pit rows equal to the radial push-pullsignal level in the groove tracks is obtained by simulation and this isformed in a graph, and an axis of abscissa shows the depth Ed [nm] ofthe embossed pit rows and an axis of ordinate shows the average dutyratio [%] of the embossed pit rows.

[0067]FIG. 7 is an example of a case that the depth Gd of the groovetracks is set at 10 nm. In FIG. 7, for example, in case of setting thedepth Ed of the embossed pit rows at 15 nm, the radial push-pull signallevel in the groove tracks is equal to the radial push-pull signal levelin the embossed pit rows when the average duty ratio of the embossed pitrows is 76%. Also, in case of setting the depth Ed of the embossed pitrows at 30 nm, both of the radial push-pull signal levels are equal whenthe average duty ratio is 36%. FIG. 7 is a graph obtained thus, and aquadratic curve in which the average duty ratio becomes the minimum whenthe depth Ed of the embossed pit rows is about 50 nm (exactly, 51.4 nm)is obtained. The quadratic curve obtained here can be approximated bythe following mathematical equation 1.

Duty=0.0461Ed²−4.720Ed+136.13   [Eq. 1]

[0068]FIG. 8 is an example of a case that the depth Gd of the groovetracks is set at 20 nm. FIG. 8 is a graph in which results simulated bythe same procedure as that described with reference to FIG. 7 areplotted. In the graph of FIG. 8, the average duty ratio of the embossedpit rows is large as a whole in comparison with the example shown inFIG. 7, and a quadratic curve in which the average duty ratio of theembossed pit rows is minimized when the depth Ed of the embossed pitrows is about 50 nm is obtained. The quadratic curve obtained here canbe approximated by the following mathematical equation 2.

Duty=0.0401Ed²−4.149Ed+164.9   [Eq. 2]

[0069] Similarly, FIG. 9 is an example of a case that the depth Gd ofthe groove tracks is set at 30 nm. The average duty ratio of theembossed pit rows is more larger in comparison with the example shown inFIG. 8, and a quadratic curve in which the average duty ratio of theembossed pit rows is minimized when the depth Ed of the embossed pitrows is about 50 nm is obtained. The quadratic curve obtained here canbe approximated by the following mathematical equation 3.

Duty=0.0423Ed²−4.353Ed+192.7   [Eq. 3]

[0070] In FIG. 10, the minimum values f (Gd) of the average duty ratioof the embossed pit rows shown in FIGS. 7 to 9 are plotted. An axis ofabscissa shows the depth Gd of the groove tracks and an axis of ordinateshows the minimum value f(Gd). A quadratic curve obtained here can beapproximated by the following mathematical equation 4.

f(Gd)=−0.07Gd²+6Gd−35.6   [Eq. 4]

[0071] Based on the mathematical equations 7 to 10, the average duty ofthe embossed pit rows in case of selecting the depth Gd of the groovetracks and the depth Ed of the embossed pit rows can be approximated bythe following mathematical equation 5.

Duty=0.04 (Ed−λ/8n)²+f(Gd) [Eq. 5]

[0072] Here, λ denotes a wavelength [nm] of a light beam and n denotes arefractive index of a substrate of the DVD-RW 10 and f(Gd) is theminimum value of the average duty ratio of the embossed pit rows and forexample, the minimum value is about 51.4 nm when a wavelength (λ) of alight beam is 650 nm and a refractive index (n) of a substrate is 1.58,and the minimum value f(Gd) becomes an intrinsic value determined by thedepth Gd of the groove tracks.

[0073] For example, when the depth Gd of the groove tracks is 30 nm andthe depth Ed of the embossed pit rows is 50 nm and λ/8n is 51.4 nm, f(Gd)=81.4 nm is obtained by the mathematical equation 4 and the averageDuty=81.4784 is obtained by the mathematical equation 5. As described inFIG. 6, this result corresponds to a result that in the case of formingthe depth Gd of the groove tracks at 30 nm, the radial push-pull signallevel on the groove tracks 11 is substantially equal to the radialpush-pull signal level on the embossed pit rows when the embossed pitrows with the average duty ratio of about 80% are formed at a depth of50 nm.

[0074] According to the DVD-RW 10 of the embodiment thus, when numericvalues satisfying the mathematical equations 4 and 5 are set in arelation among the depth Gd of the groove tracks, the depth Ed, and theaverage duty of the embossed pit rows, the radial push-pull signal levelVe on the embossed pit rows 19 can be set not to be smaller than about80% of the radial push-pull signal level Ve on the groove tracks 11certainly.

[0075] Next, an optical recording medium manufacturing apparatus 50 forcutting an optical disk master 40 necessary to manufacture the DVD-RW 10of the embodiment will be described with reference to a block diagramshown in FIG. 11.

[0076] The optical recording medium manufacturing apparatus 50 comprisesa land data generator 20, a parallel/serial converter (P/S) 21, anencoder 22 for pre-format, a clock signal generator 23, a light beamgeneration device 24, an objective lens 25, a spindle motor 26, arotation detector 27, a rotation servo circuit 28, a feeding unit 29, aposition detector 30, a feeding servo circuit 31, a controller 32, agroove data generator 33, a wobbling signal generator 34, and a switch35.

[0077] The optical disk master 40 mounted on the spindle motor 26 isformed of a glass substrate 41 and a resist layer 42 coated on thisglass substrate 41. The resist layer 42 is exposed by applying a lightbeam B described below, and pits having a shape corresponding to achange in intensity of the light beam B are formed.

[0078] In FIG. 11, the land data generator 20 outputs parallel datacorresponding to the pre-pits 13 formed on the land tracks 12 undercontrol of the controller 32. The outputted parallel data is convertedinto serial data by the parallel/serial converter 21. Then, this serialdata is inputted to the encoder 22 for pre-format to output a pre-pitformation signal SL for actually forming the pre-pits 13 on the opticaldisk master 40 to the light beam generation device 24 on a basis of aclock signal supplied from the clock signal generator 23.

[0079] On the other hand, the groove data generator 33 generates agroove formation signal SG including record data formed as the groovetracks 11 and the embossed pit rows 19 under control of the controller32 to output the signal as a control signal to the switch 35. That is,the switch 35 is turned on or off by the output signal of the groovedata generator 33.

[0080] The wobbling signal generator 34 generates a wobbling signal forproviding a slight wave to the groove tracks 11 to output the signal tothe switch 35. In the switch 35, switching control is performed on abasis of the groove data outputted from the groove data generator 33.When the switching has been done to a side of a terminal a, the wobblingsignal outputted from the wobbling signal generator 34 is outputted tothe light beam generation device 24. When the switching has been done toa side of a terminal b, an output to the light beam generation device 24is formed into a ground level.

[0081] The light beam generation device 24 emits two light beams A(shown by a dotted line in the drawing) and B (shown by a solid line inthe drawing) for forming the groove tracks 11 and the pre-pits 13 withrespect to the optical disk master 40, respectively. The light beamgeneration device 24 is a device for emitting the light beam A forforming the groove tracks 11 based on the output of the switch 35described above, and when the switch 35 has been shifted to the side ofthe terminal a, the first light beam A is deviated in a radial directionof a disk in response to a change in a level of the wobbling signaloutputted from the wobbling signal generator 34 and the groove trackportion meandering on the resist layer 42 is exposed. Also, when theswitch 35 is shifted to the side of the terminal b so that a signal fromthe switch 35 is a ground level, the light beam generation device 24stops the emission of the light beam A and stops the exposure of theresist layer 42. Thus, the embossed pit portion can be exposed on theresist layer 42 by switching the switch 35. Further, in the light beamgeneration device 24, the laser power is controlled on a basis of acontrol signal PC of the controller 32 and when the embossed pit portionis exposed, the laser power of the light beam A is increased and theresist layer 42 is exposed deeper than the groove track portion.

[0082] Also, on a basis of the pre-pit formation signal SL outputtedfrom the encoder 22 for pre-format, the light beam generation device 24turns on or off the second light beam B to expose the pre-pit portionbetween the adjacent groove track portions.

[0083] On the other hand, the spindle motor 26 rotates the optical diskmaster 40 and also the rotation detector 27 detects rotation of theoptical disk master 40. As a result of this, the rotation servo circuit28 controls rotation of the optical disk master 40 and also rotationpulses in synchronization with the rotation are outputted. The positiondetector 30 detects a position of the feeding unit 29 and outputs adetected signal to the feeding servo circuit 31. The feeding servocircuit 31 acquires position information of the feeding unit 29 based onthe detected signal from the position detector 30 and whereby servocontrol of movement of the feeding unit 29 is performed.

[0084] Next, cutting processing of the optical disk master 40 performedin the optical recording medium manufacturing apparatus 50 according tothe embodiment will be described with reference to a flowchart shown inFIG. 12. Incidentally, this processing is performed by the controller 32mainly according to a control program recorded in memory (not shown).Also, such a control program will be described by an example in whichthe groove track portion corresponding to the groove tracks 11 withrespect to the optical disk master 40 is exposed at a depth of 30 nm andthe embossed pit portion corresponding to the embossed pit rows 19 isexposed at a depth of 50 nm.

[0085] As shown in FIG. 12, when the cutting processing in the opticalrecording medium manufacturing apparatus 50 is started, the switch 35 isshifted to the side of the terminal a in order to expose the continuousgroove track portions and also the land data generator 20 is initializedin order to expose the pre-pit portion corresponding to the pre-pits 13.Also, the laser power of the light beam generation device 24 is set sothat a depth Gd of the groove becomes 30 nm (step S1).

[0086] Subsequently, exposure of the groove track portion and thepre-pit portion with respect to the optical disk master 40 is started(step S2). That is, while controlling the rotation servo circuit 28 andthe feeding servo circuit 31, the light beam generation device 24 isdriven and controlled to start exposure of the optical disk master 40 bythe first light beam A and the second light beam B. Then, addressinformation to be recorded in the pre-pit portion is referred and it isdetermined whether or not the first light beam A reaches a control datazone (step S3). Incidentally, this determination may detect whether ornot the address information becomes the head address 02F200h of thecontrol data zone as shown in FIG. 2. Then, as a result of thedetermination in step S3, if the first light beam A reaches the controldata zone (step S3: YES), an operation proceeds to step S4.

[0087] In order to expose the embossed pit portion, the groove datagenerator 33 is controlled to output control data of the average duty of80%, and also in order to set the exposure depth at 50 nm, the laserpower of the light beam generation device 24 is set high (step S4), andexposure of the embossed pit portion and the pre-pit portion withrespect to the optical disk master 40 is started (step S5).Subsequently, address information to be recorded in the pre-pit portionis referred and it is determined whether or not the first light beam Areaches a buffer zone 2 (step S6). Incidentally, this determination maydetect whether or not the address information becomes the head address02FE00h of the buffer zone as shown in FIG. 2. Then, as a result of thedetermination in step S6, if the first light beam A reaches the bufferzone (step S6: YES), an operation proceeds to step S7.

[0088] After the buffer zone 2, the continuous groove track portions andthe pre-pit portions must again be exposed at a depth of 30 nm, so thatthe groove data generator 33 is controlled to shift the switch 35 to theside of the terminal a, and the laser power of the light beam generationdevice 24 is returned to an initial value, and exposure of the groovetrack portion and the pre-pit portion with respect to the optical diskmaster 40 is performed (step S7). Then, address information to berecorded in the pre-pit portion is referred and it is determined whetheror not the first light beam A reaches the outermost circumference of theoptical disk master 40 (step S8). As a result of this determination, ifit is detected that the first light beam A reaches the outermostcircumference (step S8: YES), an operation proceeds to step S9 and stopcontrol is performed to complete a series of operation programs.

[0089] By performing the operation control described above, the groovetrack portion, the embossed pit portion and the pre-pit portioncorresponding to the spiral groove tracks 11, embossed pit rows 19 andpre-pits 13 are exposed on the optical disk master 40. Thereafter, thisoptical disk master 40 is subjected to developing treatment and theexposed portion is removed. Then, based on the optical disk master 40after this development, a stamper is formed and thereafter using thisstamper, the DVD-RW 10 in accordance with the embodiment ismass-manufactured according to a well known replication process.

[0090] Incidentally, the invention is not limited to the embodimentdescribed above. For example, according to the embodiment describedabove, the example in which the invention is applied to the DVD-RW diskis shown, but it goes without saying that the invention maybe applied toan optical recording medium of other types such as DVD-R or DVD-RAM.Also, the depth Gd of the groove tracks 11 is 50 nm and the depth Ed ofthe embossed pit rows 19 is 80 nm and the average duty is 80%, but theirvalues can take on various values based on the mathematical equations 4and 5 described above.

[0091] According to the invention, a constant radial push-pull signalcan be obtained over the whole region of a disk and an operation of aservo circuit in a recording and reproducing apparatus can always bemaintained stably.

What is claimed is:
 1. An optical recording medium capable of opticallyrecording record information, comprising: a first region formedcontinuous groove tracks thereon to be recorded the record information;and a second region formed discontinuous embossed pit rows thereon inaccordance with predetermined data, wherein the embossed pre-pits rowsprevents from reproducing data overwritten on the second region; and alevel of a radial push-pull signal of the second region is not smallerthan about 80% of a level of a radial push-pull signal of the firstregion.
 2. The optical recording medium according to claim 1, whereinthe groove tracks and the embossed pit rows substantially satisfy thefollowing mathematical equation Duty=0.04(Ed−λ/8n)²+(−0.07Gd²+6Gd−35.6)where Duty [%] is an average duty of the embossed pit rows, Ed [nm] is adepth of the embossed pit rows, λ [nm] is a wavelength of a light beam,and n is a refractive index of a substrate of the optical recordingmedium, and Gd [nm] is a depth of the groove track.
 3. An optical diskmaster manufacturing apparatus for manufacturing an optical disk masterfor manufacturing an optical recording medium capable of opticallyrecording record information, the optical recording medium comprising afirst region formed continuous groove tracks thereon to be recorded therecord information and a second region formed discontinuous embossed pitrows thereon in accordance with predetermined data, wherein the embossedpre-pits rows prevents from reproducing data overwritten on the secondregion and a level of a radial push-pull signal of the second region isnot smaller than about 80% of a level of a radial push-pull signal ofthe first region, the apparatus comprising: a light beam generator forforming a plurality of regions on the optical disk master correspondingto the first and second regions of the optical recording medium; and acontroller for controlling the light beam generator.
 4. The optical diskmaster manufacturing apparatus according to claim 3, wherein the groovetracks and the embossed pit rows of the optical recording mediumsubstantially satisfy the following mathematical equationDuty=0.04(Ed−λ/8n)²+(−0.07Gd²+6Gd−35.6) where Duty [%] is an averageduty of the embossed pit rows, Ed [nm] is a depth of the embossed pitrows, λ [nm] is a wavelength of a light beam, and n is a refractiveindex of a substrate of the optical recording medium, and Gd [nm] is adepth of the groove track.
 5. An optical disk master manufacturingmethod for manufacturing an optical disk master for manufacturing anoptical disk master for manufacturing an optical recording mediumcapable of optically recording record information, the optical recordingmedium comprising a first region formed continuous groove tracks thereonto be recorded the record information and and a second region formeddiscontinuous embossed pit rows thereon in accordance with predetermineddata, wherein the embossed pre-pits rows prevents from reproducing dataoverwritten on the second region and a level of a radial push-pullsignal of the second region is not smaller than about 80% of a level ofa radial push-pull signal of the first region, the method comprising thesteps of forming a plurality of regions on the optical disk mastercorresponding to the first and second regions of the optical recordingmedium.
 6. The optical disk master manufacturing method according toclaim 5, wherein the groove tracks and the embossed pit rows of theoptical recording medium substantially satisfy the followingmathematical equation Duty=0.04(Ed−λ/8n)²+(−0.07Gd²+6Gd - 35.6) whereDuty [%] is an average duty of the embossed pit rows, Ed [nm] is a depthof the embossed pit rows, λ [nm] is a wavelength of a light beam, and nis a refractive index of a substrate of the optical recording medium,and Gd [nm] is a depth of the groove track.